Valves, such as throttle valves, are often employed to regulate fluid flow streams in engines. Engines inherently vibrate and subject the throttle valves to varying thermal loads. Some engines, such as diesel engines being designed for forthcoming regulatory standards, can subject the flapper assembly to considerable forces thereby causing a large torque on the rotatable shaft. These environmental factors can be problematic for the valves.
Typically, the valves have small parts, such as screws, to fasten fluid control surfaces to valve bodies. These small parts can be in the flow stream. For example, butterfly valves typically have a flapper assembly that is disposed in a valve body. The flapper assembly is usually comprised of two vanes that are coupled, directly or indirectly, to a rotatable shaft in the valve body with fasteners. The vanes and shaft and, therefore, the screws are in the flow stream. Other configurations of the control surfaces, such as a flapper configuration where the shaft is offset from the center of the valve, also have fasteners in the flow stream.
The engine's vibration, varying thermal loads, and large torque can cause the fasteners to loosen over time, even if securely fastened. As a result, the fasteners can enter the flow stream and fall into the engine causing catastrophic damage. For example, if a screw falls through an intake manifold on an engine, it could enter an engine cylinder with an intake and exhaust poppet valves. The screw could, in one failure mode, cause the poppet valves to lodge open in chamber. A piston in the cylinder could then stroke towards the poppet valve to compress air-fuel mixture. However, instead of compressing the air-fuel mixture, the piston strikes the poppet valve that is lodged open by the screw. This will destroy the piston which in turn causes a catastrophic failure of the engine.
Therefore, each loose part in the fluid flow has a potential high associated cost. Fasteners can be improved so they are not prone to loosen due to the environmental factors. However, designing fasteners for the vibration, thermal loads, and high torque is expensive due to the low volume of such fasteners. Eliminating parts from the throttle valve can therefore eliminate the associated high cost of each failure mode as well as the high costs of specially designed fasteners.
Accordingly, there is a need to eliminate fasteners from the throttle valves. There is also a need to eliminate fasteners from the flapper assemblies.